1. Field of the Invention
The present invention relates to reproduction of recorded data on an optical disc, and more particularly, to a method and apparatus of detecting the BCA of an optical disc.
2. Description of the Prior Art
The latest DVD discs comprise an area known as a burst cutting area (BCA), which is an annular area near the center of the disc, containing ID codes and manufacturing information recorded after the end of the disc manufacturing process. The purpose of the code recorded in the BCA is to form a link between the content of the disc and the software to be used with that disc. The BCA is a series of stripes in a bar code like shape on the surface of the disc, formed utilizing a high power laser to partially remove an aluminum reflective layer of the disc.
Please refer to FIG. 1, which is a table illustrating a BCA structure according to the prior art. The BCA structure consists of a BCA preamble, a data field including information data, an error detection code (EDC) EDCBCA, an error correction code (ECC) ECCBCA, and a BCA postamble. The BCA preamble includes a sync byte SBBCA and four following bytes PR0-PR3. The sync byte SBBCA contains a fixed sync pattern and a specific sync code, where the sync code has a sync ID 0. The sync byte SBBCA indicates the start position of the BCA. The information data field consists of information blocks, each comprising 4 resync bytes RSBCA1, . . . , RSBCAn having the same sync ID, and 16 information bytes, wherein each resync byte RSBCA1, . . . , RSBCAn includes a fixed sync pattern and a specific sync code, and is followed by four information bytes respectively. For example, four information bytes I0, I1, I2, I3 follow the resync byte RSBCA1. According to the BCA specification, the sync byte SBBCA and the resync bytes RSBCA1-RSBCA15 have the same fixed sync pattern expressed in channel bits as “01000110”. The error detection code EDCBCA consists of 4 bytes D0, D1, D2, D3, and the error correction code ECCBCA consists of 16 bytes C0,0-C3,3, where resync bytes RSBCA13 with sync ID 13 precede the error correction code ECCBCA. The postamble having four bytes PO0-P03 is preceded by a resync byte RSBCA14 with sync ID 14 and followed by a resync byte RSBCA15 with sync ID 15.
As mentioned above, the sync byte SBBCA is used to indicate the start of the BCA. Once it has been detected, demodulating of the BCA can begin. The prior art uses a phase locked loop (PLL) to extract a clock that is synchronized with the BCA bit cycle, in order to detect the sync byte. The data processor detects the fixed sync pattern based on the generated clock, and then determines whether or not the sync ID is 0. Once the start position of the BCA has been confirmed (i.e. ID of the detected sync pattern is determined to be 0) and data acquisition has begun, the data processor can begin to decode the acquired data. As shown in FIG. 1, the data bytes between the BCA preamble and the BCA postamble are extracted and decoded. In addition, the EDC procedure is activated to check if error bits exist by utilizing the EDCBCA, and the ECC procedure is activated to correct error bits of the decoded BCA data.
The system can only begin to decode data when the sync byte SBBCA is detected; if the sync byte RSBCA cannot be detected due to some defects, decoding cannot take place. Furthermore, the PLL must be synchronized with the BCA channel bit cycle in order to detect the sync byte SBBCA, so any deviation from this synchronization will also cause the decoding operation to fail.